Days after the leak stopped, Chevron told the state’s office of emergency services it had released 220 pounds of ammonia into the air each day for 11 days beginning in June. But the oil company didn’t tell the South Coast Air Quality Management District about the leak as state law requires. The district learned of the spill from KPCC.

Reached by e-mail, a Chevron spokesman said the release didn’t affect refinery operations, and didn’t endanger people. The El Segundo plant has a permit to release some ammonia into the air. But local regulators set limits on that because ammonia combines with other gases to form particulate matter and smog.

That poses respiratory concerns for people nearby. Particulates also can change climate and contribute to global warming. The air quality district has asked Chevron for more information. Chevron says it’s working with appropriate agencies to resolve the matter.